Inkjet printers typically utilize a printhead that includes an array of orifices (also called nozzles) through which ink is ejected on to paper or other print media. One or more printheads may be mounted on a movable carriage that traverses back and forth across the width of the paper feeding through the printer. Alternatively, one or more printheads may be mounted on a stationary carriage, as in a page-wide printhead array. A printhead may be an integral part of an ink cartridge or part of a discrete assembly to which ink is supplied from a separate, often replaceable ink container. For printhead assemblies that utilize replaceable ink containers, it is desirable to keep the outlet from the ink container sealed during packaging, shipping and storage to prevent ink leaking from the container.